Global shipper FedEx (NYSE:FDX), as key a macro bellwether as there is, confirmed the funk Tuesday when it took yet another hatchet to its earnings outlook. And that came part and parcel of FDX posting its first quarterly earnings decline since 2009.

FedEx did a decent job managing the market’s expectations, but the biggest threats to the rally and economy won’t be so considerate. Because as soon as one crisis at home or abroad recedes from the headlines, another threat boils up.

Europe is back in the headlines over fear that Spain will wait too long to ask for bailout aid.

The Middle East, always a cauldron of uncertainty, has flared up — again. Violent and deadly uprisings have spread from Libya to as far away as Indonesia.

And, of even more concern to markets, is escalating tension between Israel and Iran. A new survey by Business Insider reveals that a geopolitical shock sending oil prices skyrocketing is among the most frequently cited worries keeping market pros up at night.

Moreover, that oil shock could be set off from someplace other than Iran and the Strait of Hormuz, Cumberland Advisors’ David Kotok told Business Insider. He’s more worried about rising extremism and civil war in Nigeria, which is the most important producer in the world.

Whatever sets it off, an oil-price shock would be more than sufficient to push the global economy decidedly into recession. And if it were to coincide with the automatic tax hikes and spending cuts of the Jan. 1 fiscal cliff?

Look out below.

Ah, but it gets even worse.

Everyone knew China’s economy was cooling dramatically — the question is whether it would manage a hard landing or a soft one. But now questions over leadership in the world’s second-largest economy have further muddied the outlook.

The top Chinese leader might have recently reappeared after going missing from public view, but waves of protests against Japan aren’t very reassuring as to what’s happening internally among the Communist Party elite.

Furthermore, Fitch — the third-biggest rating agency after Moody’s (NYSE:MCO) and Standard & Poor’s (NYSE:MHP) — warned that the credit ratings in Japan’s auto and tech sectors could be at risk of downgrade if relations further deteriorate between the world’s second- and third-largest economies.

Yes, central bank easing in the U.S. and Europe might have stocks at levels last seen in late 2007, but September also is historically the most bearish month for equity performance. Stocks have come very far, very fast. The shorts, presumably, have covered.

Why does it feel like we’re just one big, bad headline away from a pullback?

As of this writing, Dan Burrows did not hold a position in any of the aforementioned securities.